fix: EM when selecting External RF mode PPM (#6909)

Co-authored-by: Peter Feerick <5500713+pfeerick@users.noreply.github.com>

radio/src/targets/common/arm/stm32/module_timer_driver.cpp

@@ -58,8 +58,21 @@ static void module_timer_send(void* ctx, const etx_timer_config_t* cfg,
   stm32_pulse_start_dma_req(timer, pulses, length, ocmode, ocval);  
 }
 
+static bool module_timer_tx_complete(void* ctx)
+{
+  auto tim = (const stm32_pulse_timer_t*)ctx;
+
+  if (LL_DMA_IsEnabledStream(tim->DMAx, tim->DMA_Stream)) 
+  {
+    return false;
+  }
+
+  return true;
+}
+
 const etx_timer_driver_t STM32ModuleTimerDriver = {
   .init = module_timer_init,
   .deinit = module_timer_deinit,
   .send = module_timer_send,
+  .txCompleted = module_timer_tx_complete
 };

radio/src/targets/simu/module_drivers.cpp

@@ -122,10 +122,13 @@ static void module_timer_send(void* ctx, const etx_timer_config_t* cfg,
                               const void* pulses, uint16_t length)
 {}
 
+static bool module_timer_tx_completed(void* ctx) { return true; }
+
 const etx_timer_driver_t _fakeTimerDriver = {
   .init = module_timer_init,
   .deinit = module_timer_deinit,
   .send = module_timer_send,
+  .txCompleted = module_timer_tx_completed,
 };
 #endif